Semiconductor device and manufacturing method thereof

ABSTRACT

There is disclosed a semiconductor device comprising a first wire and a pad portion thereof provided in a portion from an upper surface to an inner portion of a first insulation film provided above a substrate, a second insulation film provided on the first insulation film and the first wire, a second wire provided to be exposed from an upper surface of the second insulation film in an upper portion of the pad portion of the first wire, and a contact plug provided to reach an inner portion of the pad portion of the first wire from an undersurface of the second wire.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2002-309871, filed Oct. 24, 2002, the entire contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates to a technique of improving the reliability of a semiconductor device. More specifically, the present invention relates to a semiconductor device including pad portions improved in structure, and to a manufacturing method thereof.

[0004] 2. Description of the Related Art

[0005] In general, various semiconductor elements formed in a semiconductor substrate (Si wafer) are electrically connected via wires (metal wires). Known techniques for forming such metal wires include a technique by which, for example, grooves are formed by applying patterning and anisotropic etching to an insulation film formed on an Si wafer, and copper (Cu) used as a line material is then filled in the grooves. A metal wire formed by such a technique is generally called a “Cu damascene wire.”

[0006] Generally, the surface of the Cu damascene wire is apt to be oxidized. As such, for example, in the event of applying a bonding material onto a pad portion of the Cu damascene wire formed in a semiconductor element, when the surface of the Cu damascene wire is oxidized, the electric resistance is apt to rise at a contact between the pad portion and the bonding material. In addition, since Cu damascene wires are generally soft, when, for example, a needle of a probe used to perform electrical measurement is dropped onto a pad portion of the Cu damascene wire from an upper portion thereof, the needle can easily stick into the surface of the Cu damascene wire. Oxidation develops from a needle-stuck point, thereby causing the electric resistance to increase. To prevent the problem, aluminum (Al) wires are used to form top-layer wires onto Cu damascene wires. Generally, an Al wire has a higher oxidation resistance and hardness than Cu damascene wire. For these reasons, pad portions are formed of Al wires, not Cu damascene wires.

[0007] However, in a contact portion (connection portion) between a Cu damascene wire and an Al wire, Cu is apt to penetrate into Al. To prevent the problem, a barrier metal film (BM film) formed of a material having a high barrier property for preventing the penetration of Cu into Al needs to be provided between Cu damascene wires and Al wires. Generally, a barrier metal film between Cu damascene wires and Al wires is formed using TaN. Nevertheless, when the Cu damascene wire and the Al wires are connected to each other via the barrier metal film (TaN film) formed of TaN, connected portions therebetween tend to peel off from each other. A technique for preventing such inter-film peel is disclosed in, for example, Japanese Unexamined Patent Application Publication No. 10-98039.

BRIEF SUMMARY OF THE INVENTION

[0008] According to an aspect of the present invention, there is provided a semiconductor device comprising: a first wire and a pad portion thereof provided in a portion from an upper surface to an inner portion of a first insulation film provided above a substrate; a second insulation film provided on the first insulation film and the first wire; a second wire provided to be exposed from an upper surface of the second insulation film in an upper portion of the pad portion of the first wire; and a contact plug provided to reach an inner portion of the pad portion of the first wire from an undersurface of the second wire.

[0009] According to another aspect of the present invention, there is provided a manufacturing method of a semiconductor device, comprising: forming a recess for a first wire and a recess for a pad portion of the first wire; forming the recess for the first wire in a portion from an upper surface of a first insulation film provided above a substrate to an inner portion thereof; forming the recess for the pad portion of the first wire in continuation to the recess for the first wire while selectively leaving the first insulation film; forming the first wire and the pad portion of the first wire by burying a first conductive material into inner portions of the recess for the first wire and the recess for the pad portion of the first wire; providing a second insulation film onto the first insulation film wherein the first wire and the pad portion of the first wire are formed; forming a recess for a second wire and a contact hole by removing the second insulation film on the pad portion of the first wire and the first insulation film selectively left; and forming the second wire and a contact plug by burying a second conductive material into inner portions of the recess for a second wire and the contact hole.

[0010] According to still another aspect of the present invention, there is provided a manufacturing method of a semiconductor device, comprising: forming a recess for a first wire and a recess for a pad portion of the first wire; forming the recess for the first wire in a portion from an upper surface of a first insulation film provided above a substrate to an inner portion thereof; forming the recess for the pad portion of the first wire in continuation to the recess for the first wire while the first insulation film is selectively left; forming the first wire and the pad portion of the first wire by burying a first conductive material into inner portions of the recess for the first wire and the recess for the pad portion of the first wire; providing a second insulation film onto the first insulation film wherein the first wire and the pad portion of the first wire are formed; forming a contact hole by removing the first insulation film selectively left and second insulation film existing thereon; forming a contact plug by burying a second conductive material into an inner portion of the contact hole; providing a third insulation film on the second insulation film wherein the contact plug is formed; forming a recess for the second wire by removing the third insulation film existing on the pad portion of the first wire such that an upper surface of the contact plug is exposed; and forming the second wire by burying a third conductive material into an inner portion of the recess for the second wire.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

[0011]FIG. 1A is a cross-portional view showing an in-process state of a semiconductor device in a manufacturing method according to a first embodiment of the present invention;

[0012]FIG. 1B is a cross-portional view showing an in-process state of the semiconductor device in the manufacturing method according to the first embodiment;

[0013]FIG. 1C is a plan view showing the in-process state of the semiconductor device in the manufacturing method according to the first embodiment;

[0014]FIG. 2A is a cross-portional view showing an in-process state of the semiconductor device in the manufacturing method according to the first embodiment;

[0015]FIG. 2B is a cross-portional view showing an in-process state of the semiconductor device in the manufacturing method according to the first embodiment;

[0016]FIG. 2C is a plan view showing the in-process state of the semiconductor device in the manufacturing method according to the first embodiment;

[0017]FIG. 3A is a cross-portional view showing an in-process state of the semiconductor device in the manufacturing method according to the first embodiment;

[0018]FIG. 3B is a cross-portional view showing an in-process state of the semiconductor device in the manufacturing method according to the first embodiment;

[0019]FIG. 3C is a plan view showing an in-process state of the semiconductor device in the manufacturing method according to the first embodiment;

[0020]FIG. 4A is a cross-portional view showing an in-process state of the semiconductor device in the manufacturing method according to the first embodiment;

[0021]FIG. 4B is a plan view showing an in-process state of the semiconductor device in the manufacturing method according to the first embodiment;

[0022]FIG. 5A is a cross-portional view showing an in-process state in a manufacturing method of a semiconductor device according to a second embodiment of the present invention;

[0023]FIG. 5B is a cross-portional view showing an in-process state of the semiconductor device in the manufacturing method according to the second embodiment;

[0024]FIG. 5C is a cross-portional view showing an in-process state of the semiconductor device in the manufacturing method according to the second embodiment;

[0025]FIG. 6A is a cross-portional view showing an in-process state of the semiconductor device in the manufacturing method according to the second embodiment;

[0026]FIG. 6B is a plan view showing an in-process state of the semiconductor device in the manufacturing method according to the second embodiment;

[0027]FIG. 7A is a cross-portional view showing an in-process state in a manufacturing method of a semiconductor device according to a third embodiment of the present invention;

[0028]FIG. 7B is a cross-portional view showing an in-process state of the semiconductor device in the manufacturing method according to the third embodiment;

[0029]FIG. 7C is a cross-portional view showing an in-process state of the semiconductor device in the manufacturing method according to the third embodiment;

[0030]FIG. 8A is a cross-portional view showing an in-process state of the semiconductor device in the manufacturing method according to the third embodiment;

[0031]FIG. 8B is a cross-portional view showing an in-process state of the semiconductor device in the manufacturing method according to the third embodiment;

[0032]FIG. 8C is a cross-portional view showing an in-process state of the semiconductor device in the manufacturing method according to the third embodiment;

[0033]FIG. 9A is a cross-portional view showing an in-process state of the semiconductor device in the manufacturing method according to the third embodiment;

[0034]FIG. 9B is a plan view showing an in-process state of the semiconductor device in the manufacturing method according to the third embodiment;

[0035]FIG. 10A is a cross-portional view showing an in-process state of the semiconductor device in a manufacturing method according to a fourth embodiment of the present invention;

[0036]FIG. 10B is a cross-portional view showing an in-process state of the semiconductor device in the manufacturing method according to the fourth embodiment;

[0037]FIG. 10C is a cross-portional view showing an in-process state of the semiconductor device in the manufacturing method according to the fourth embodiment;

[0038]FIG. 10D is a cross-portional view showing an in-process state of the semiconductor device in the manufacturing method according to the fourth embodiment;

[0039]FIG. 11A is a cross-portional view showing an in-process state of the semiconductor device in the manufacturing method according to the fourth embodiment;

[0040]FIG. 11B is a cross-portional view showing an in-process state of the semiconductor device in the manufacturing method according to the fourth embodiment;

[0041]FIG. 11C is a cross-portional view showing an in-process state of the semiconductor device in the manufacturing method according to the fourth embodiment;

[0042]FIG. 12A is a cross-portional view showing an in-process state of the semiconductor device in the manufacturing method according to the fourth embodiment;

[0043]FIG. 12B is a plan view showing an in-process state of the semiconductor device in the manufacturing method according to the fourth embodiment;

[0044]FIG. 13A is a plan view showing a semiconductor device by way of a comparative example with respect to the first embodiment;

[0045]FIG. 13B is a cross-portional view showing a semiconductor device by way of a comparative example with respect to the first embodiment;

[0046]FIG. 14A is a plan view showing another semiconductor device by way of comparative example with respect to the first embodiment; and

[0047]FIG. 14B is a cross-portional view showing another semiconductor device by way of comparative example with respect to the first embodiment.

DETAILED DESCRIPTION OF THE INVENTION

[0048] The present invention will be described in detail hereinbelow with reference to illustrated embodiments.

FIRST EMBODIMENT

[0049] Before description of a first embodiment of the present invention, the problems with the related art described above will be described in more detail with reference to comparative examples with respect to the first embodiment.

[0050] In general, Cu is apt to penetrate into Al in the contact portion (connection portion) between the Cu damascene wire and the Al wire according to the related art described above. To prevent the problem, a barrier metal film (BM film) formed of a material having high barrier property for preventing the penetration of Cu into Al needs to be provided between Cu damascene wires and Al wires. Generally, a barrier metal film between Cu damascene wires and Al wires is formed using TaN. Nevertheless, when the Cu damascene wire and the Al wires are connected to each other via the barrier metal film (TaN film) formed of TaN, connected portions therebetween tend to peel off from each other. This will be described hereinbelow with reference to the drawings.

[0051] Referring to FIGS. 13A and 13B, in a semiconductor device 101, a Cu damascene wire 104 and a TaN barrier metal film 105 are formed in an inner portion of an n-th interlayer insulation film 103 (n=1 or greater integer) provided above a semiconductor substrate 102. A diffusion barrier film 106 and an insulation film 107 formed as an uppermost layer are provided onto the Cu damascene wire 104 and the interlayer insulation film 103. An Al wire 109 is formed near a pad portion opening portion 108 formed to pass through the diffusion barrier film 106 and an insulation film 107. Concurrently, the Al wire 109 is formed such that the undersurface thereof is in planar and indirect contact with the upper surface of the Cu damascene wire 104 via the TaN barrier metal film 105. In this manner, a pad portion 110 of the semiconductor device 101 is formed of the Cu damascene wire 104 and the Al wire 109 that is provided immediately above the Cu damascene wire 104 to be in planar contact therewith. FIG. 13B is a cross-portional view of the semiconductor device taken along the single-dotted chain line X-X of FIG. 13A.

[0052] A needle of a probe (not shown) is dropped over the pad portion 110 of the semiconductor device 101. Thereby, there might be a case in which the Cu damascene wire 104 and the Al wire 109 peel off from each other at a contact portion (connection portion) therebetween. To prevent such inter-wire peel, a semiconductor device 201 is formed to include pad portions structured as shown in FIGS. 14A and 14B. A technique of this type for preventing such inter-wire peel is disclosed in, for example, Japanese Unexamined Patent Application Publication No. 10-98039.

[0053] Similarly to the case of the semiconductor device 101 described above, in a semiconductor device 201, a Cu damascene wire 204 and a TaN barrier metal film 205 are formed in an inner portion of an n-th interlayer insulation film 203 provided above a semiconductor substrate 202. A diffusion barrier film 206 and an insulation film 207 formed as an uppermost layer are provided onto the Cu damascene wire 204 and the interlayer insulation film 203. An Al damascene wire 209 is formed above the Cu damascene wire 204 to be in indirect contact with the upper surface of the Cu damascene wire 204 via the TaN barrier metal film 205. The Al damascene wire 209 is formed of a wire main body portion 209 a and via-plugs 209 b integrally formed in the wire main body portion 209 a. Thus, the Al via-plug 209 b is not a single large via-plug, but the plurality of small via-plugs 209 b are formed. Each of the via-plugs 209 b is formed by depositing an Al film 213 in a via-hole 208 b. The each via-plug 209 b is formed such that the undersurface thereof is in indirect contact with the upper surface of the Cu damascene wire 204. Thus, a pad portion 210 of the semiconductor device 201 is formed of the Al damascene wire main body portion 209 a, the individual via-plugs 209 b, and the Cu damascene wire 204. FIG. 14B is a cross-portional view of the semiconductor device taken along the single-dotted chain line Y-Y of FIG. 14A.

[0054] Thus, as the semiconductor device 201, it is effective for a semiconductor device to employ the structure of the type in which planar interwire contact does not take place in order to prevent peel between the Cu damascene wire 204 and the Al damascene wire 209 in the pad portion 210. In addition, it is effective to employ the structure of the type in which the insulation films 206 and 207 are held between the Cu damascene wire 204 and the Al damascene wire 209 in order to improve the interwire adhesive property.

[0055] Generally, however, in many cases, a pad portion has wires formed in direct contact with power supply lines. In this case, depending on the semiconductor element formed in the substrate, there might be a case in which high current is supplied to flow into the pad portion. In comparison to the semiconductor device 101, in the semiconductor device 201, the area of contact between the Cu damascene wire 204 and the insulation film 207 is reduced. As compared with the Al pad portion 110 of the semiconductor device 101, immunity resistance against electromigration (EM), for example, may be deteriorated in the pad portion 210 of the semiconductor device 201.

[0056] Further, in a configuration in which multi-layer wires are formed onto a semiconductor element by forming Cu damascene wires in via-holes and grooves formed by processing an insulation film, when current is applied to the multi-layer wires for long time, conduction failure can occur at via-plugs. The defects are caused by the occurrence of electromigration resulting from the movement of Cu along the direction of the flow of electrons. Electromigration failure tends to occur with the interface of TaN barrier metal film between a Cu wire and a via-plug. Especially, electromigration failure is facilitated to occur resulting from the movement of Cu in the lower-layer Cu damascene wire immediately below the via-plug when electrons flow from the via-plug side to the side of the lower-layer Cu damascene wire via the barrier metal film. Particularly, conduction failure occurs resulting from the movement of Cu in a corner portion of the via-plug at which the electric fields tend to be concentrated. Accordingly, an object required to increase the electromigration immunity is therefore to increase the area of contact between the lower-layer Cu damascene wire and the via-plug via the barrier metal film.

[0057] The first embodiment of the present invention is designed to solve the problems described above. The object of the first embodiment is to provide a semiconductor device improved in interwire adhesive property in a pad portion, interwire electric conductivity, and reliability. Another object is to provide a method of manufacturing a semiconductor device capable of manufacturing such a semiconductor device. This will be described in detail hereinbelow.

[0058] Referring to FIGS. 1A to 4B, the first embodiment of the present invention will now be described hereunder. FIGS. 1A to 3C are cross-portional views and plan views each showing an in-process state of a semiconductor device in a manufacturing method according to the first embodiment. FIGS. 4A and 4B are a cross-portional view and a plan view, respectively, showing an in-process state of the semiconductor device and the manufacturing method according to the first embodiment. The semiconductor device of the present embodiment and the manufacturing method thereof will be described along the sequence of manufacturing steps.

[0059] With reference to FIG. 1A, an n-th interlayer insulation film 2 (n=1 or greater integer) is provided as a first insulation film above a silicon substrate 1 (an Si substrate or a semiconductor substrate) in which active regions, lower-layer wires, and the like, which configure various electronic circuits (not shown), are formed. More specifically, the first interlayer insulation film 2 is deposited above the surface of the silicon substrate 1 up to a thickness of about 0.5 μm by a process such as CVD. The first embodiment employs an SiO₂ film as the interlayer insulation film 2. In the first embodiment, one layer of the interlayer dielectric film 2 is formed above the silicon substrate 1. However, a multi-layer wire structure may be formed such that a plurality of interlayer insulation films 2 are laminated, and wires are formed in the individual interlayer insulation films 2. In such a multi-layer wire structure, a first wire 6 (described below) is formed as a top layer of the interlayer insulation films 2.

[0060] Subsequently, referring to FIGS. 1B and 1C, a recess for a first wire 3 is formed to form a first wire 6 on the interlayer insulation film 2 (SiO₂ film). More specifically, a wiring pattern of the first wire 6 is patterned on the surface of the SiO₂ film 2 by a process such as a photoresist process. Then, the SiO₂ film 2 is processed by anisotropic etching using CF gas, and the recess 3 is thereby formed. For the anisotropic etching, an RIE (reactive ion etching) process is employed.

[0061] To etch the SiO₂ film 2, the SiO₂ film 2 is processed such that the recess 3 has a depth d (FIG. 1B) of about 0.4 μm and a width w (FIG. 1C) of about 0.4 μm. In the recess 3, the SiO₂ film 2 is processed to a predetermined size and shape to selectively remain in inner portions of recesses for a pad portion of the first wire 3 a in which the pad portion 6 a of the first wire 6 are formed. In the first embodiment, as shown in FIGS. 1B and 1C, the SiO₂ film 2 is etched such that a total of 36 substantially four-sided columnar SiO₂ films 2 a remain in matrix (6 pieces along each of vertical and horizontal lines) in the recesses 3 a. In this case, each of the SiO₂ films 2 a etched to selectively remain is formed slightly smaller than the size of each contact hole 9 b (described below) that is formed based on the SiO₂ film 2 a. More specifically, the each SiO₂ film 2 a is formed to have a height of about 0.4 μm and to have a plan-view size of about 0.015 μm×0.015 μm. The each SiO₂ film 2 a in the recesses 3 a hereinbelow will be referred to as “residual SiO₂ film 2 a.” FIG. 1B is a cross-portional view of the semiconductor device taken along the single-dotted chain line A-A of FIG. 1C.

[0062] Subsequently, with reference to FIG. 2A, a barrier metal film 4 and a material for forming the first wire 6 are sequentially laminated onto the surface of the SiO₂ film 2 and in the individual inner portions of the recess 3 and the recesses 3 a. More specifically, the barrier metal film 4 is first deposited by a process such as a PVD (physical vapor deposition) process on the surface of the SiO₂ film 2 and the inner portion of the recess 3. For the barrier metal film 4, the present embodiment employs a TaN film (conductive ceramic layer). Subsequently, a first conductive material for forming the first wire 6 is deposited also by a PVD process onto the surface of the TaN film 4. In the present embodiment, the first wire 6 is formed by an electroplating process using copper (Cu). More specifically, a Cu plating seed layer (film) (not shown) to be used as a base of the first wire 6 is deposited onto the surface of the TaN film 4. Thereafter, a Cu film 5 used as a material for forming the first wire 6 is deposited onto the surface of the Cu plating seed layer in such a manner as to fill the inner portion of the recess 3. In this case, the TaN film 4 and the Cu plating seed layer are individually used as electrodes.

[0063] Subsequently, with reference to FIGS. 2B and 2C, unnecessary portions of the TaN film 4 and Cu film 5 are removed. More specifically, the unnecessary portions of the TaN film 4 and Cu film 5 are polished and removed by a CMP (chemical mechanical polishing) process. In this manner, unnecessary portions of the TaN film 4 and the Cu film 5, that is, portions present outside the recess 3 and the recesses 3 a, are removed from the upper portions of the SiO₂ film 2. Thereby, the TaN film 4 and the Cu film 5 are left only in the inner portions of the recess 3 and the recesses 3 a. That is, the barrier metal film 4 made of TaN and the Cu film 5 are buried in the SiO₂ film 2. Consequently, the so-called Cu damascene wire 6 is formed as the first wire in the inside of the SiO₂ film 2. In this case, the pad portions 6 a of the Cu damascene wire 6 are also formed in the inside of the SiO₂ film 2. Hereinbelow, the each pad portion 6 a of the Cu damascene wire 6 is referred to as a “Cu pad portion 6 a.” FIG. 2B is a cross-portional view of the semiconductor device taken along the single-dotted chain line B-B of FIG. 2C.

[0064] Subsequently, referring to FIG. 3A, a diffusion barrier film 7 (capping layer) and a second insulation film 8 (used as an (n+1)th interlayer insulation film) are sequentially laminated onto the surface of the SiO₂ film 2 in which the Cu damascene wire 6 and the like are formed. The second insulation film 8 functions as a pad portion insulation film. The present embodiment employs an SiN film as the diffusion barrier film 7, and employs an SiO₂ film as the second insulation film 8. The SiN film 7 and the SiO₂ film 8 are each deposited by a process such as a CVD process to a desired thickness.

[0065] Subsequently, referring to FIGS. 3B and 3C, a recess for a second wire 9 a and contact holes 9 b (via-holes) are formed in regions from the SiO₂ film 8 onto the Cu pad portions 6 a to the residual SiO₂ film 2 in the Cu pad portions 6 a. These recess 9 a and the contact holes 9 b are used to form a second wire 12 a and contact plugs 12 b (via-plugs), which will be described below. In the present first embodiment, the contact plugs 12 b are formed integrally with the second wire 12 a. Specifically, the second wire 12 a is formed to be a so-called dual damascene structure (dual damascene wire). As such, the recess 9 a is integrally formed in connection to the contact holes 9 b.

[0066] In more detail, the recess 9 a and the contact holes 9 b are formed by a process such as an RIE process that etches and removes the residual SiO₂ film 2 a, the SiN film 7 on the residual SiO₂ film 2 a, and the SiO₂ film 8 on the Cu pad portions 6 a. The recess 9 a is formed to substantially pass through all the SiO₂ film 8 and SiN film 7 on the Cu pad portion 6 a. However, the SiN film 7 on the Cu pad portions 6 a is left to prevent oxidation and diffusion of the Cu pad portions 6 a. The each contact hole 9 b is formed by removing the residual SiO₂ film 2 a in the Cu pad portion 6 a. Concurrently, the each contact hole 9 b is formed to have a plan-view size of about 0.2 μm×0.2 μm. That is, the each contact hole 9 b is formed slightly larger in plan-view size than the each four-sided columnar SiO₂ film 2 a.

[0067] In addition, in the present embodiment, the each contact hole 9 b is formed to have the bottom portion (lower end portion) positioned at substantially the same height as the bottom portion (undersurface) of the pad portion 6 a of the Cu damascene wire 6. That is, the each contact hole 9 b is formed to pass through the Cu pad portion 6 a. Thereby, the contact plug 12 b is formed to have the bottom portion (lower end portion) positioned at substantially the same height as the bottom portion (undersurface) of the Cu pad portion 6 a of the Cu damascene wire 6. More specifically, the each contact hole 9 b is formed to a depth of about 0.4 μm that is substantially the same as the thickness of the Cu pad portion 6 a of the Cu damascene wire 6. Thereby, the contact plug 12 b is formed to a length of about 0.4 μm that is substantially the same as the thickness of the Cu pad portion 6 a of the Cu damascene wire 6.

[0068] Either one of the recess 9 a and the contact holes 9 b may be formed earlier than the other. When the contact holes 9 b is formed earlier than the recess 9 a, the residual SiO₂ film 2 a and the SiN film 7 and SiO₂ film 8 on the residual SiO₂ film 2 a are first etched and removed. Subsequently, a material such as a mask material (not shown) is provided to prevent the SiN film 7 on the Cu pad portions 6 a from being etched. Then, the SiO₂ film 8 remaining on the Cu pad portions 6 a is etched and removed. When the recess 9 a is formed earlier than the contact holes 9 b, the SiO₂ film 8 on the Cu pad portions 6 a is first etched and removed. Subsequently, a material such as a mask material (not shown) is provided to prevent the SiN film 7 on the Cu pad portions 6 a from being etched. Then, the residual SiO₂ film 2 a and the SiN film 7 on the residual SiO₂ film 2 a are etched and removed. FIG. 3B is a cross-portional view of the semiconductor device taken along the single-dotted chain line C-C of FIG. 3C.

[0069] Subsequently, referring to FIGS. 4B and 4C, a barrier metal film 10, which is an independent object from the TaN film 4, and a forming material for the second wire 12 a are sequentially laminated onto the surface of the SiO₂ film 8 and in inner portions of the recess 9 a and contact holes 9 b. More specifically, the barrier metal film 10 is first deposited by a process such as a PVD process on the surface of the SiO₂ film 8 and in the inner portions of the recess 9 a and contact holes 9 b. Similar to the case of the barrier film 4, the present embodiment employs a TaN film (conductive ceramic layer) as the barrier metal film 10. Subsequently, a second conductive material for forming the second wire 12 a is deposited also by a PVD process onto the surface of the TaN film 10. In the present embodiment, the second wire 12 a is formed by using aluminium (Al). Accordingly, an Al film 11 is deposited onto the surface of the TaN film 10 in such a manner as to fill the inner portions of the recess 9 a and contact holes 9 b to a desired thickness.

[0070] Subsequently, unnecessary portions of the TaN film 10 and Al film 11 are removed. More specifically, a wiring pattern of the second wire 12 a is patterned on the surface of the Al film 11 by a process such as a photoresist process. Thereafter, a process such as an RIE process is applied to process the TaN film 10 and the Al film 11 for removing unnecessary portions of the TaN film 10 and Al film 11. Thereby, the TaN film 10 and the Al film 11 are buried in the recess 9 a, and the second wire 12 a is formed. Concurrently, the TaN film 10 and the Al film 11 are buried in the contact holes 9 b, and the contact plugs 12 b are formed. Consequently, the second wire 12 a is formed to be a dual damascene structure formed integrally with the contact plugs 12 b by using Al. Thus, a so-called Al dual damascene wire 12 a is formed as the second wire 12 a onto the pad portions 6 a of the Cu damascene wire 6. Description hereinbelow may use the name “Al pad portion 12 c” to refer to a portion of the Al damascene wire 12 a above Al contact plugs 12 b and the Cu pad portions 6 a. Also, the Al dual damascene wire 12 a may simply be referred to as “Al damascene wire 12 a.”

[0071] Referring to FIG. 4A, the Al damascene wire 12 a is formed such that the undersurface is in indirect contact with the upper surface of the Cu pad portions 6 a via the TaN film 10 and the SiN film 7. Concurrently, the each Al contact plug 12 b is formed to have the bottom portion (lower end portion) positioned at substantially the same height as the bottom portion (undersurface) of the Cu pad portion 6 a. The each Al contact plug 12 b is formed to a length of about 0.4 μm that is substantially the same as the thickness of the Cu pad portion 6 a. Thus, the each Al contact plugs 12 b is formed such that the outer portion (outer surface) thereof is in contact with an inner portion (inner surface) of the Cu pad portions 6 a via the TaN film 4 and the TaN film 10. In this manner, the Al pad portion 12 c is formed in the shape to be fitted to the Cu pad portions 6 a via the Al contact plug 12 b formed to substantially pass through the Cu pad portions 6 a. That is, the Al pad portion 12 c and the Cu pad portions 6 a are formed to be non-planar contact with each other.

[0072] Subsequently, predetermined steps are carried out, and a desired semiconductor device 14 is obtained, referring to FIGS. 4A and 4B. The semiconductor device 14 has a pad portion 13 structured such that the Al damascene wire 12 a and the Cu damascene wire 6 are in three-dimensional contact (connection) with each other in the respective Cu pad portions 6 a and Al damascene wire 12 a. The Al damascene wire 12 a is electrically connected to the Cu damascene wire 6 mainly via the Al contact plugs 12 b. FIG. 4A is a cross-portional view along with the single-dotted chain line D-D of FIG. 4B.

[0073] Description is now provided hereinbelow regarding manufacturing methods of comparative examples and tests performed by the inventors and the results of the tests with reference to FIGS. 4A, 4B, 13A, 13B, and 14A, and 14B. The tests were performed to evaluate reliability of the semiconductor device which was formed of the Cu wire whose pad portions were different in their materials and the Al wire, in two aspects, the one being the structure and the other being the electrode characteristics.

[0074] Semiconductor devices represented by the semiconductor devices 14 shown in FIGS. 4A and 4B and described above were selected by way of first samples (according to the first embodiment). Second samples were selected from semiconductor devices represented by the related-art semiconductor device 101 shown in FIGS. 13A and 13B. Third samples were selected from semiconductor devices represented by the related-art semiconductor device 201 shown in FIGS. 14A and 14B. The semiconductor devices 101 and 201 are comparative examples (comparative samples) with respect to the semiconductor device 14. Hereinbelow, the manufacturing method of each of the semiconductor devices 101 and 201 selected by way of as the comparative examples of the two types will be concisely described along the sequence of manufacturing steps.

FIRST COMPARATIVE EXAMPLE

[0075] Referring to FIGS. 13A and 13B, an SiO₂ film 103 is deposited as an interlayer insulation film by a process such as CVD process to a thickness of about 0.5 μm above an Si substrate 102 in which active regions configuring various electronic circuits (not shown), lower-layer wires, and the like are formed. Subsequently, a wiring pattern of a Cu damascene wire 104 is patterned on the surface of the SiO₂ film 103 by a photoresist process. Then, the SiO₂ film 103 is processed by anisotropic etching (RIE processing) using a CF gas, and a recess for the Cu damascene wire 111 is thereby formed. In this case, the SiO₂ film 103 is processed to the extent that a depth d1 of the recess 111 shown in FIG. 13B is about 0.4 μm, and a width w1 of the recess 111 shown in FIG. 13A is about 0.2 μm.

[0076] A TaN film 105, which works as a barrier metal film, and a Cu film 112, which is used as a material for forming the Cu damascene wire 104, are sequentially laminated by a PVD process onto the surface of the SiO₂ film 103 and in an inner portion of the recess 111. The Cu film 112 is formed in the following manner. First, a Cu plating seed layer (film) (not shown) to be used as a base is deposited onto the surface of the TaN film 105. Thereafter, the Cu film 112 is deposited in such a manner as to fill the inner portion of the recess 111. In this case, the TaN film 105 and the Cu plating seed layer are individually used as electrodes. Subsequently, portions of the TaN film 105 and Cu film 112 above the surface of the SiO₂ film 103 are polished and removed. In this manner, the TaN film 105 and the Cu film 112 are buried in the SiO₂ film 103, and the Cu damascene wire 104 is thereby formed.

[0077] Subsequently, an SiN film 106, which works as a diffusion barrier film (capping layer), and an SiO₂ film 107, which works as a pad portion insulation film, are sequentially laminated by a CVD process onto the SiO₂ film 103, the Cu damascene wire 104, and the like. Subsequently, a single pad portion opening portion 108 (a contact hole or via-hole) is formed by an RIE process to a plan-view size of about 40 μm×40 μm, which is slightly smaller than the size of a Cu pad portion 104 a. The opening portion 108 is formed to pass through the SiN film 106 and the SiO₂ film 107 above the Cu pad portion 104 a of the Cu damascene wire 104.

[0078] Subsequently, the TaN film 105, which works as a barrier metal film, and an Al film 113, which is used as a material for forming the Al wire 109, are sequentially laminated by a PVD process onto the surface of the SiO₂ film 107 and in an inner portion of the pad portion opening portion 108. Then, a wiring pattern of the Al wire 109 is patterned by a photoresist processing on the surface of the Al film 113. Thereafter, the TaN film 105 and the Al film 113 are processed by an RIE process, and unnecessary portions of the TaN film 105 and the Al film 113 are removed. Thereby, the Al wire 109 is formed. Of the Al wire 109, a portion that is in indirect contact with the Cu damascene wire 104 via the TaN film 105 is used as a pad portion 109 a of the Al wire 109. The Al pad portion 109 a can be regarded as one large via-plug (contact plug) formed in the Al wire 109.

[0079] Referring to FIGS. 13A and 13B, in the semiconductor device 101, the Cu damascene wire 104 and the Al wire 109 are in indirect and substantially planar contact with each other via the TaN film 105 in the Cu pad portion 104 a and the pad portion 109 a (Al via-plug or Al contact plug). That is, the pad portion 110 of the semiconductor device 101 is structured such that the Cu damascene wire 104 and the Al wire 109 are in indirect and substantially planar contact with each other via the TaN film 105. FIG. 13B is a cross-portional view of the semiconductor device taken along the single-dotted chain line X-X of FIG. 13A.

SECOND COMPARATIVE EXAMPLE

[0080] Referring to FIGS. 14A and 14B, an SiO₂ film 203 is deposited as an interlayer insulation film by a process such as a CVD process to a thickness of about 0.5 μm above an Si substrate 202 in which active regions configuring various electronic circuits (not shown), lower-layer wires, and the like are formed. Subsequently, a wiring pattern of a Cu damascene wire 204 is patterned on the surface of the SiO₂ film 203 by a photoresist process. Then, the SiO₂ film 203 is processed by anisotropic etching (RIE processing) using a CF system gas, and a recess for the Cu damascene wire 211 is thereby formed. In this case, the SiO₂ film 203 is processed to the extent that a depth d2 of the recess 211 shown in FIG. 14B is about 0.4 μm, and a width w2 of the recess 211 shown in FIG. 14A is about 0.2 μm.

[0081] A TaN film 205, which works as a barrier metal film, and a Cu film 212, which is used as a material for forming the Cu damascene wire 204, are sequentially laminated by a PVD process onto the surface of the SiO₂ film 203 and in an inner portion of the recess 211. The Cu film 212 is formed in the following manner. First, a Cu plating seed layer (film) (not shown) to be used as a base is deposited onto the surface of the TaN film 205. Thereafter, the Cu plating seed layer is deposited in such a manner as to fill the inner portion of the recess 211. In this case, the TaN film 205 and the Cu plating seed layer are individually used as electrodes. Subsequently, portions of the TaN film 205 and Cu film 212 above the surface of the SiO₂ film 203 are polished and removed. In this manner, the TaN film 205 and the Cu film 212 are buried in the SiO₂ film 203, and the Cu damascene wire 204 is thereby formed.

[0082] Subsequently, an SiN film 206, which works as a diffusion barrier film (capping layer), and an SiO₂ film 207, which works as a pad portion insulation film, are sequentially laminated by a CVD process onto the SiO₂ film 203, the Cu damascene wire 204, and the like. Then, the SiN film 206 and the SiO₂ film 207 above a Cu pad portion 204 a of the Cu damascene wire 204 are processed by an RIE process, and recesses for the damascene wire 208 a and via-holes 208 b (contact holes) are thereby formed. In the semiconductor device 201, via-plugs 209 b are formed integrally with a damascene wire 209 a. Specifically, the Al damascene wire 209 a is formed to be a so-called dual damascene structure (dual damascene wire). The recesses 208 a are formed integrally with the via-holes 208 b in continuation thereto.

[0083] In the semiconductor device 201, the pad portion 210 is formed to a plan-view size of about 40 μm×40 μm. In the pad portion 210, 400 Al via-plugs 209 b each having a plan-view size of about 1 μm×1 μm are formed. Accordingly, 400 via-holes 208 b each having a plan-view size of 1 μm×1 μm are formed within a region of about 40 μm×40 μm. FIG. 14A shows only 36 of 400 Al via-plugs 209 b for the purpose of simplicity.

[0084] Subsequently, the TaN film 205, which works as a barrier metal film, and an Al film 213, which is used as a material for forming the damascene wire 209 a and the via-plugs 209 b, are sequentially laminated by a PVD process onto the surface of the SiO₂ film 207 and in individual inner portions of the recesses 208 a and the via-holes 208 b. Then, a wiring pattern of the damascene wire 209 a is patterned by a photoresist process on the surface of the Al film 213. Thereafter, the TaN film 205 and the Al film 213 are processed by an RIE process, and unnecessary portions of the TaN film 205 and the Al film 213 are removed. Thereby, an Al dual damascene wire 209 a integrated with the via-plugs 209 b is formed as an Al dual damascene wire 209 (which hereinbelow will simply be referred to as the “Al damascene wire 209.”). Of the Al damascene wire 209 a, a portion above the Al via-plugs 209 b and the Cu pad portions 204 is used as a pad portion 209 c of the Al damascene wire 209.

[0085] As shown in FIGS. 14A and 14B, in the semiconductor device 201, the lower end portions of the 400 Al via-plugs 209 b and the upper surface of the Cu pad portion 204 a are in indirect contact with each other via the TaN film 205. More specifically, in comparison with the pad portion 110 of the semiconductor device 101 formed as the first comparative example, the structure of the first comparative example is characterized in that the Cu pad portion 204 a and the pad portion 209 c are substantially in indirect point contact with each other via the TaN film 205. Consequently, the contact area between the Cu damascene wire 204 and the Al damascene wire 209 a is reduced, in comparison with the pad portion 110 of the semiconductor device 101 of the first comparative example. However, to secure a sufficient adhesion property between the Cu damascene wire 204 and the Al damascene wire 209 a, the SiN film 206 and the SiO₂ film 207 are left (held) between the individual Al via-plugs 209 b and between the Cu damascene wire 204 and the Al damascene wire 209 a. FIG. 14B is a cross-portional view of the semiconductor device taken along the single-dotted chain line Y-Y of FIG. 14A.

[0086] Tests were conducted to examine mechanical strengths and electrical characteristics of the above-described first to third samples, namely, the pad portions 13, 110, and 210 (Al pad portions 12 c, 109 a, and 209 c) of the respective semiconductor devices 14, 101, and 201, under the same conditions.

[0087] First, with regard to 100 semiconductor devices 14 according to the first embodiment, the mechanical strengths of pad portions 13 (Al pad portions 12 c) were evaluated. As a result, no peel was verified to occur between the individual Al damascene wires 12 a and Cu damascene wires 6 in all the pad portions 13. With regard to 100 semiconductor devices 14, the electromigration (EM) immunities were evaluated for all the pad portions 13. As a result, the tolerable current density was verified to be 8 mA/um² in each of the all pad portions 13.

[0088] Subsequently, with regard to 100 semiconductor devices 101 of the first comparative examples, the mechanical strengths of pad portions 110 (Al pad portions 109 a) were evaluated. As a result, in the pad portion 110 of each of the 10 semiconductor devices 101, peel was verified to occur at the interface between the TaN film 105, which is provided between the Al damascene wire 109 and the Cu damascene wire 104, and the upper surface of the Cu damascene wire 6. In addition, with regard to 100 semiconductor devices 14, electromigration (EM) immunities of the all pad portions 110 were evaluated. As a result, the tolerable current density was verified to be 4 mA/um² in each of the all pad portions 110, which was lower than that in the first embodiment. Concurrently, the service life was verified to be short.

[0089] Subsequently, with regard to 100 semiconductor devices 201 of the second embodiment, the mechanical strengths of pad portions 210 (Al pad portions 209 c) were evaluated. As a result, in the pad portion 210 of each of the all semiconductor devices 201, no peel was verified to occur between the Al damascene wire 209 and the Cu damascene wire 204. In addition, with regard to 100 semiconductor devices 201, electromigration (EM) immunities of the all pad portions 210 were evaluated. As a result, the tolerable current density was verified to be 2 mA/um² in each of the all pad portions 210, which was further lower than that in the first embodiment. Concurrently, the service life was verified to be short, as in the case of the first comparative example.

[0090] As described above, according to the first embodiment, the Al dual damascene wire 12 a is formed such that the undersurface thereof is in indirect contact with the upper surfaces of the Cu pad portions 6 a (Cu damascene wire 6) in the Al pad portion 12 c. In addition, the each Al contact plug 12 b is formed such that the outer surface thereof is in indirect contact with the inner surface of the corresponding Cu pad portion 6 a. More specifically, the each Al contact plug 12 b is formed such that the cross portion thereof is shaped like a so-called wedge or a comb toothing and is fitted to the Cu pad portion 6 a. Consequently, the Al dual damascene wire 12 a and the Cu damascene wire 6 are formed to be three-dimensional and in indirect contact with each other.

[0091] The thus-structured semiconductor device 14 according to the first embodiment has an increased area of contact between the Al dual damascene wire 12 a and the Cu damascene wire 6 in the pad portion 13. Accordingly, the present embodiment exhibits improved adhesive property (adhesive strength) between the Al dual damascene 12 a and the Cu damascene wire 6 in the pad portion 13, as compared with the semiconductor device according to the related art in which the Al wire and the Cu wire are in planar contact with each other in the pad portion. In addition, the present embodiment exhibits a reduced current density per unit area in the pad portion 13. Thereby, the embodiment is improved in electromigration immunity and is hence improved in the electric conductivity between the Al dual damascene wire 12 a and the Cu damascene wire 6.

[0092] In more detail, in the semiconductor device 14, there occurs no undesired case in which peel occurs on the interface between conductors such as the Al dual damascene wire 12 a and the Cu damascene wire 6 in the pad portion 13, and appropriate EM immunity can be secured therein. Thus, the semiconductor device 14 of the present embodiment is improved in the adhesive property and electric conductivity between wires in the pad portion 13 and is consequently improved in reliability. Further, according to the manufacturing method of the semiconductor device of the present embodiment, the manufacture of the semiconductor device 14 described above can easily be implemented.

SECOND EMBODIMENT

[0093] Referring to FIGS. 5A to 6B, a second embodiment of the present invention will now be described hereunder. FIGS. 5A to 5C are cross-portional views each showing an in-process state of a semiconductor device in a manufacturing method according to the second embodiment. FIGS. 6A and 6B are a cross-portional view and a plan view, respectively, each showing an in-process state of the semiconductor device and the manufacturing method thereof according to the second embodiment. The same numerals are used to refer to the same portions as those in the first embodiment, and detailed description thereof will be omitted therefrom.

[0094] As in the first embodiment, the second wire is formed to be a dual damascene structure in the second embodiment. The semiconductor device according to the present embodiment and the manufacturing method thereof will be described collectively along the sequence of manufacturing steps.

[0095] With reference to FIG. 5A, using steps similar to those in the first embodiment, an SiN film 7 and an SiO₂ film 8 are sequentially laminated onto an SiO₂ film 2 in which a Cu damascene wire 6 and the like are formed.

[0096] Subsequently, referring to FIG. 5B, a recess for a second wire 22 a and contact holes 22 b are formed in portions extending from the upper surface of the SiO₂ film 8 on the Cu pad portion 6 a to the inner portions of the residual SiO₂ film 2 in the Cu pad portions 6 a. Similarly to the second wire 12 a in the first embodiment described above, also a second wire 25 a is formed in integration with contact plugs 25 b. In the present embodiment, the contact plugs 25 b are formed integrally with the second wire 25 a. Specifically, the second wire 25 a is formed to be a dual damascene structure (dual damascene wire). As such, the recess 22 a is integrally formed in connection to the contact holes 22 b.

[0097] In more detail, the recess 22 a and the contact holes 22 b are formed by etching and removing residual SiO₂ film 2 a, the SiN film 7 on the residual SiO₂ film 2 a, and the SiO₂ film 8 on the Cu pad portions 6 a. In this case, the recess 22 a is formed by removing a SiO₂ film 8 from its upper surface (surface) to its inner portion (intermediate portion) in an upper portion 6 a. That is, the recess 22 a is formed in such a form not to penetrate into the SiO₂. Accordingly, the SiN film 7 and SiO₂ are left on the Cu pad portion 6 a. Thus, the second wire 25 a is formed such that the under surface thereof is spaced apart from the upper face of the pad portion 6 a of the Cu damascene 6 working as the first wire.

[0098] The contact holes 22 b are formed by etching and removing the residual SiO₂ film 2 a, the SiN film 7 on the residual SiO₂ film 2 a, and the SiO₂ film 8 on the residual SiO₂ film 2 a to communicate with the bottom portion of the recess 22 a. Similar to the each contact hole 9 b in the first embodiment, the each contact hole 22 b in the present embodiment is also formed to have the bottom portion (undersurface) positioned at substantially the same height as the bottom portion (undersurface) of the Cu pad portion 6 a. That is, the each contact hole 22 b is formed to pass through the Cu pad portion 6 a. Similar to the recess 9 a and the contact holes 9 b in the first embodiment, either one of the recess 22 a and the contact holes 22 b may be formed earlier than the other.

[0099] Subsequently, referring to FIG. 5C, a barrier metal film 23 (TaN film), which is an independent object from the TaN film 4, and a forming material for the second wire 25 a are sequentially laminated onto the surface of the SiO₂ film 8 and in individual inner portions of the recess 22 a and contact holes 22 b. More specifically, the TaN film 23, which works as the barrier metal film, is first deposited by a PVD process on the surface of the SiO₂ film 8 and in the individual inner portions of the recess 22 a and contact holes 22 b. Subsequently, an Al film 24 to be used as a forming material for the second wire 25 a is deposited also by a PVD process onto the surface of the TaN film 23 in such a manner as to fill the individual inner portions of the recess 22 a and contact holes 22 b to a desired thickness.

[0100] Subsequently, referring to FIG. 6A, unnecessary portions of the TaN film 23 and Al film 24 are removed. More specifically, a wiring pattern of the second wire 25 a is patterned on the surface of the Al film 24 by a process such as a photoresist process. Thereafter, a process such as an RIE process is applied to process the TaN film 23 and the Al film 24 for removing unnecessary portions of the TaN film 23 and Al film 24. Thereby, the TaN film 23 and the Al film 24 are buried in the recess 22 a, and the second wire 25 a is formed. Concurrently, the TaN film 23 and the Al film 24 are buried in the contact holes 22 b, and the contact plugs 25 b are formed. Consequently, the second wire 25 a is formed to be a dual damascene structure formed integrally with the contact plugs 25 b by using Al. Thus, an Al dual damascene wire 25 a is formed as the second wire 25 a above the pad portions 6 a of the Cu damascene wire 6. Description hereinbelow may use the name “Al pad portion 25 c” to refer to a portion of the Al dual damascene wire 25 a above the Al contact plugs 25 b and the Cu pad portions 6 a. Also, the Al dual damascene wire 25 a may simply be referred to as the “Al damascene wire 25 a.”

[0101] Subsequently, predetermined steps are carried out, and a semiconductor device 21 is obtained, as shown in FIGS. 6A and 6B. Specifically, the semiconductor device 21 has a pad portion 26 structured such that the undersurface of the Al pad portion 25 c is spaced apart from the upper surface of the Cu pad portions 6 a. In addition, the Al pad portion 25 c and the Cu damascene wire 6 are in three-dimensional contact (connection) with each other via the Al contact plugs 25 b. The Al damascene wire 25 a is electrically connected to the Cu damascene wire 6 via the Al contact plugs 25 b. FIG. 6A is a cross-portional view along with the single-dotted chain line E-E in FIG. 6B.

[0102] As described above, according to the second embodiment, advantages similar to those of the first embodiment can be obtained. Portions of the SiN film 7 and the SiO₂ film 8 are left on the Cu pad portions 6 a. That is, a multilayer film of insulation films formed of the SiN film 7 and the SiO₂ film 8 is sandwiched (held) between the undersurface of the Al pad portion 25 c and the upper surfaces of the Cu pad portions 6 a. This improves the adhesive property (adhesion) between the Cu pad portions 6 a and the Al pad portion 25 c. Consequently, the durability and reliability in the pad portion 26 of the semiconductor device 21 are further improved.

THIRD EMBODIMENT

[0103] Referring to FIGS. 7A to 9B, a third embodiment will now be described hereunder. FIGS. 7A to 8C are cross-portional views each showing an in-process state of a semiconductor device in a manufacturing method according to the third embodiment. FIGS. 9A and 9B are a cross-portional view and a plan view, respectively, each showing an in-process state of the semiconductor device and the manufacturing method thereof according to the third embodiment. The same numerals are used to refer to the same portions as those in the first embodiment, and detailed description thereof will be omitted therefrom.

[0104] The present embodiment is different from the first and second embodiments in that the second wire is formed to be a so-called single damascene structure. The semiconductor device according to the present embodiment and the manufacturing method thereof will be described collectively along the sequence of manufacturing steps.

[0105] With reference to FIG. 7A, using steps similar to those in the first and second embodiments, an SiN film 7 and an SiO₂ film 8 are sequentially laminated onto an SiO₂ film 2 in which a Cu damascene wire 6 and the like are formed. Subsequently, contact holes 32 b are formed in portions extending from the upper surface of the SiO₂ film 8 to the inner portions of the residual SiO₂ film 2 in the Cu pad portions 6 a. Then, a second wire 35 a of the present embodiment is formed separately from contact plugs 35 b in, as described above, a different manner from the cases of the second wire 12 a of the first embodiment and the second wire 25 a of the second embodiment. The second wire 35 a of this embodiment is formed to be a so-called single damascene structure (single damascene wire). Accordingly, the contact holes 32 b are formed as independent objects from a recess for the second wire 32 a. In detail, the contact holes 32 b are formed by an RIE process that etches and removes the residual SiO₂ film 2 a, the SiN film 7 on the residual SiO₂ film 2 a, and the SiO₂ film 8 on the Cu pad portions 6 a. The contact holes 32 b are thus formed to pass through the residual SiO₂ film 2 a, the SiN film 7 on the residual SiO₂ film 2 a, and the SiO₂ film 8 on the residual SiO₂ film 2 a. Similar to the each of the contact holes 9 b and 22 b in the respective first and second embodiments, the each contact hole 32 b in the present embodiment is also formed to have the bottom portion (lower end portion) positioned at substantially the same height as the undersurface (lower end portion) of the Cu pad portion 6 a. That is, the each contact hole 32 b is formed to pass through the Cu pad portion 6 a.

[0106] Subsequently, referring to FIG. 7B, a barrier metal film 33 which is an independent object from the TaN film 4, and a forming material for the contact plugs 35 b are sequentially laminated on the surface of the SiO₂ film 8 and the contact holes 32 b. More specifically, the TaN film 33, which works as the barrier metal film, is first deposited by a PVD process on the surface of the SiO₂ film 8 and in the individual inner portions of the contact holes 32 b. Subsequently, an Al film 34 (second conductive material) to be used as a forming material for the contact plugs 35 b is deposited also by a PVD process onto the surface of the TaN film 33 in such a manner as to fill the individual inner portions of the contact holes 32 b to a desired thickness.

[0107] Subsequently, referring to FIG. 7C, unnecessary portions of the TaN film 33 and Al film 34 are removed. More specifically, the unnecessary portions of the TaN film 33 and the Al film 34 are polished and removed by a CMP process. Thereby, the TaN film 33 and the Al film 34 are buried in the contact holes 32 b, and the contact plugs 35 b are thereby formed.

[0108] Subsequently, referring to FIG. 8A, a third insulation film 36 is formed by a process such as a CVD process to a desired thickness onto the SiO₂ film 8 in which the contact plugs 35 b and the like are formed. The present embodiment employs an SiO₂ film for the third insulation film 36.

[0109] The recess 32 a is then formed above the contact plugs 35 b, that is, above the Cu pad portions 6 a, as shown in FIG. 8B. More specifically, only an SiO₂ film 36 portion above the Cu pad portions 6 a is etched and removed by a process such as an RIE process to allow the surfaces of the SiO₂ film 8 and the contact plugs 35 b to be exposed. Thereby, recess 32 a is formed to pass through the SiO₂ film 36. In addition, portions of the SiN film 7 and the SiO₂ film 8 are left on the Cu pad portions 6 a. Thereby, the second wire 35 a is formed such that the undersurface thereof is spaced apart from the upper surface of the pad portions 6 a of the Cu damascene wire 6 that works as the first wire.

[0110] Subsequently, referring to FIG. 8C, a forming material for the second wire 35 a is provided on the surface of the SiO₂ film 36 and in the inner portion of the recess 32 a. In more detail, a film 37 of a third conductive material, which is to be used as a forming material for the second wire 35 a, is formed by a PVD process to a desired thickness on the surface of the SiO₂ film 8 and in the inner portion of the recess 32 a. In the present embodiment, the second wire 35 a is formed of the same Al material as for the contact plugs 35 b. Accordingly, the same Al material as the second conductive material is used for the third conductive material. That is, the film 37 formed of Al is formed on the surface of the SiO₂ film 8 and in the inner portion of the recess 32 a. In addition, in the present embodiment, since both the second wire 35 a and contact plugs 35 b are formed of Al, a barrier metal film need not be formed around the second wire 35 a.

[0111] Subsequently, referring to FIG. 9A, unnecessary portions of the Al film 37 is removed. More specifically, a wiring pattern of the second wire 35 a is patterned on the surface of the Al film 37 by a photoresist process. Thereafter, a process such as an RIE process is applied to process the Al film 37 for removing unnecessary portions of the Al film 37. Thereby, the Al film 37 is buried in the recess 32 a, and the second wire 35 a is formed. Consequently, the second wire 35 a is formed to be a single damascene structure formed as an independent object from the contact plugs 35 b by using Al. Thus, an Al single damascene wire 35 a is formed as the second wire 35 a onto the pad portions 6 a of the Cu damascene wire 6. Description hereinbelow may use the name “Al pad portion 35 c” to refer to a portion of the Al single damascene wire 35 a above the Al contact plugs 35 b and the Cu pad portions 6 a. Also, the Al single damascene wire 35 a may simply be referred to as the “Al damascene wire 35 a.”

[0112] Subsequently, predetermined steps are carried out, and a semiconductor device 31 is obtained, as shown in FIGS. 9A and 9B. Specifically, the semiconductor device 31 has a pad portion 38 structured such that the second wire 35 a is formed to be the single damascene structure. In addition, the undersurface of the Al pad portion 35 c is spaced apart from the upper surface of the Cu pad portions 6 a, and the Al pad portion 35 c and the Cu pad portions 6 a are in three-dimensionally contact (connection) with each other via the Al contact plugs 35 b. The Al damascene wire 35 a is electrically connected to the Cu damascene wire 6 via the Al contact plugs 35 b. FIG. 9A is a cross-portional view along with the single-dotted chain line F-F in FIG. 9B.

[0113] As described above, according to the third embodiment, while the Al damascene wire 35 a as the second wire is formed to be the single damascene structure, advantages similar to those of the individual first and second embodiments can be obtained.

FOURTH EMBODIMENT

[0114] Referring to FIGS. 10A to 12B, a fourth embodiment of the present invention will now be described hereunder. FIGS. 10A to 11C are cross-portional views each showing an in-process state of a semiconductor device in a manufacturing method according to the fourth embodiment. FIGS. 12A and 12B are a cross-portional view and a plan view, respectively, each showing an in-process state of the semiconductor device and the manufacturing method according to the fourth embodiment. The same numerals are used to refer to the same portions as those in the fourth embodiment, and detailed description thereof will be omitted herefrom.

[0115] As in the individual first and second embodiments, the second wire is formed to be a dual damascene structure in the fourth embodiment. However, only one contact plug is formed in the present embodiment. The semiconductor device according to the present embodiment and the manufacturing method thereof will be described collectively along the sequence of manufacturing steps.

[0116] With reference to FIG. 10A, using steps similar to those in the first embodiment, an SiO₂ film 2 is deposited above the surface of an Si substrate 1. Subsequently, a wiring pattern of a first wire 45 is patterned on the surface of the SiO₂ film 2 by a photoresist process. Then, the SiO₂ film 2 is processed by an RIE process, and a recess for the first wire 42 is thereby formed. In this step, the SiO₂ film 2 is etched such that only one substantially four-sided columnar residual SiO₂ film 2 a is formed in an inner portion of a recess for a pad portion of the first wire 42 a.

[0117] Subsequently, referring to FIG. 10B, a TaN film 43 working as a barrier metal film is first deposited by a PVD process onto individual inner portions of the recess 42 and the recess 42 a that are formed above the surface of the SiO₂ film 2. Subsequently, a Cu plating seed layer (film) (not shown) to be used as a base of the first wire 45 is deposited onto the surface of the TaN film 43 also by the PVD process. Thereafter, a Cu film 44 (first conductive material) used as a forming material for the first wire 45 is deposited onto the surface of the Cu plating seed layer in such a manner as to fill the individual inner portions of the recess 42 and the recess 42 a.

[0118] Subsequently, with reference to FIG. 10C, unnecessary portions of the TaN film 43 and Cu film 44 are polished and removed by a CMP process. Then, the TaN film 43 and the Cu film 44 are buried in the recess 42 and the recess 42 a. Thereby, a Cu damascene wire 45 working as the first wire and a Cu pad portion 45 a therefor are formed. In this case, the first wire 45 and the Cu pad portion 45 a are formed parallel to each other.

[0119] Subsequently, referring to FIG. 10D, an SiN film 7 and an SiO₂ film 8 working as a second insulation film are sequentially laminated onto the surface of the SiO₂ film 2 in which the Cu damascene wire 45 and the like are sequentially laminated.

[0120] Next, referring to FIG. 11A, a contact hole 46 b is formed in a region extending from the SiO₂ film 8 above the Cu pad portion 45 a to the residual SiO₂ film 2 in the Cu pad portion 45 a. In more detail, the contact hole 46 b is formed by a process such as an RIE process that etches and removes the residual SiO₂ film 2 a, the SiN film 7 on the residual SiO₂ film 2 a, and the SiO₂ film 8 on the SiO₂ film 2. Also in the present embodiment, the contact hole 46 b is formed to have the bottom portion (lower end portion) positioned at substantially the same height as the undersurface (lower end portion) of the Cu pad portion 45 a as in the respective holes 9 b, 22 b, and 32 b of the above described first to third embodiments. That is, the contact hole 46 b is formed to pass through the Cu pad portion 45 a.

[0121] Subsequently, referring to FIG. 11B, a recess for a second wire 46 a is formed above the contact hole 46 b. As in the second wires 12 a and 25 a of the respective first and second embodiments, also a second wire 49 a is formed integrally with a contact plug 49 b. That is, the second wire 49 a is formed to be a dual damascene structure (dual damascene wire). As such, the recess 46 a is integrally formed in connection to the contact hole 46 b. In more detail, the SiO₂ film 8 is etched and removed from its upper surface (surface) to the inner portion by an RIE method so as to extend the opening portion of the contact hole 46 b. Thus, the recess 46 a for passing through the upper end portion of the contact hole 46 b is formed.

[0122] The recess 46 a is formed in the shape not to pass through the SiO₂ film 8. That is, portions of the SiN film 7 and the SiO₂ film 8 are left on the Cu pad portion 45 a. Consequently, the second wire 49 a is formed such that the undersurface thereof is spaced away from the upper surface of the of the pad portions 45 a of the Cu damascene wire 6 (first wire). Similar to the recess 9 a and the contact holes 9 b in the first embodiment and the recess 22 a and the contact holes 22 b in the second embodiment, either one of the recess 46 a and the contact holes 46 b may be formed earlier than the other.

[0123] Subsequently, referring to FIG. 11C, a barrier metal film 47, which is an independent object from the barrier metal film 43, and a forming material for the second wire 49 a are sequentially laminated onto the surface of the SiO₂ film 8 and in individual inner portions of the recess 46 a and contact hole 46 b. More specifically, the TaN film 47, which works as the barrier metal film, is first deposited by a PVD process on the surface of the SiO₂ film 8 and in the individual inner portions of the recess 46 a and contact hole 46 b. Subsequently, an Al film 48 (second conductive material) to be used as a forming material for the second wire 49 a is deposited also by a PVD process onto the surface of the TaN film 47 in such a manner as to fill the individual inner portions of the recess 46 a and contact hole 46 b to a desired thickness.

[0124] Subsequently, referring to FIG. 12A, unnecessary portions of the TaN film 47 and Al film 48 are removed. More specifically, a wiring pattern of the second wire 49 a is patterned on the surface of the Al film 48 by a process such as a photoresist process. Thereafter, a process such as an RIE process is applied to process the TaN film 47 and the Al film 48 for removing unnecessary portions of the TaN film 47 and Al film 48. Thereby, the TaN film 47 and the Al film 48 are buried in the recess 46 a, and the second wire 49 a is formed. Concurrently, the TaN film 47 and the Al film 48 are buried in the contact hole 46 b, and the contact plug 49 b is formed. Consequently, the second wire 49 a is formed to be a dual damascene structure formed integrally with the contact plug 49 b by using Al. Thus, an Al dual damascene wire 49 a is formed as the second wire 49 a above the pad portions 45 a of the Cu damascene wire 45. Description hereinbelow may use the name “Al pad portion 49 c” to refer to a portion of the Al dual damascene wire 49 a above the Al contact plug 49 b and the Cu pad portions 6 a. Also, the Al dual damascene wire 49 a may simply be referred to as the “Al damascene wire 49 a.”

[0125] Subsequently, predetermined steps are carried out, and a semiconductor device 41 is obtained, as shown in FIGS. 12A and 12B. The semiconductor device 41 has a pad portion 50 structured such that the undersurface of the Al pad portion 49 c is spaced apart from the upper surface of the Cu pad portion 45 a. In addition, the Al pad portion 49 c and the Cu pad portion 45 a are in three-dimensional contact (connection) with each other via the one contact plug 49 b. The Al damascene wire 49 a is electrically connected to the Cu damascene wire 6 via the one contact plug 49 b. FIG. 12A is a cross-portional view along with the single-dotted chain line G-G of FIG. 12B.

[0126] As described above, according to the fourth embodiment, even with the one Al contact plug portion 49 b, the Al damascene wire 49 a and the Cu damascene wire 45 are in three-dimensional contact with each other. Further, the insulation film is sandwiched (held) between the undersurface of the Al pad portion 49 c and the upper surfaces of the Cu pad portions 6 a. Consequently, advantages similar to those of the individual first to third embodiments described above can be obtained.

[0127] The semiconductor device and the manufacturing method according to the present invention are not limited by the individual first to fourth embodiments described above. The configurations or manufacturing steps thereof may be executed by being partly modified to those with various settings or may be used in appropriate combinations of the individual settings.

[0128] For example, the length of the contact plug is not limited to be substantially the same as the thickness of the first wire. The length of the contact plug may be shorter or longer than the thickness of the first wire. The length may be optionally determined as long as the first and second wires can be in three-dimensional contact with each other. However, with the contact plug formed to a length longer than the thickness of the first wire, the contact plug is brought into indirect contact with the first insulation film, thereby enabling the adhesive property (adhesive strength) between the second wire and the first wire to be even further improved.

[0129] The shape of the contact plug is not limited to the four-sided columnar shape. The shape may be any one of round columnar, elliptical columnar, triangular columnar, and polygonal columnar shapes. The plug portion of the second wire may be formed to any one of plan-view shapes like, for example, a predetermined letter, figure, and numeral individually formed of a linear or nonlinear shape. That is, the plug portion may be formed in any shape as long as the plug portion allows the second wire and the first wire to be in three-dimensional contact with each other. The number of the contact plugs may be set to an appropriate value depending on the necessity.

[0130] The second wire needs not to be formed of an aluminium monomer. The second wire may be formed of any material having a high electric conductivity and a sufficient oxidation resistance. For example, in the second wire, the main body portion to be exposed to the atmosphere may be formed of a compound containing aluminium. In the second wire having the single damascene structure according to the third embodiment, the main body portion and plug portion thereof may be individually formed of different materials.

[0131] The pad portion of the first wire and the contact hole formed in the inner portion thereof may be formed in steps different from those disclosed in the individual first to fourth embodiments. Example modified steps are described hereunder. When the first wire pad portion is formed, the first insulation film in the recesses for the pad portion is completely removed, and the recesses for the pad portion are then fully filled with the first conductive material. Thereby, the first wire pad portions are formed. In this stage, the first insulation film does not remain in the first wire pad portions. Thereafter, contact holes of desired size, shape, and quantity are formed in the first wire pad portion. In addition, the contact hole may be formed before the second insulation film and the like are provided onto the first wire pad portion. In this case, a predetermined portion of the first wire pad portion is removed by, for example, etching, to form the contact hole. Subsequently, the second insulation film and the like are provided onto the first wire pad portion. Then, the recess for the second wire are formed by etching and removing the second insulation film to be connected to the contact hole. When the inner portion of the contact hole is filled (blocked) with the second insulation film and the like, the second insulation film and the like may be concurrently removed. By these steps, similar to the cases of the individual first to fourth embodiments, the desired contact hole(s) and the recesses for the second wire can be formed.

[0132] Alternatively, before the second insulation film and the like are provided onto the first wire pad portion, a mask member is provided on the contact hole such that the inner portion of the contact hole is not filled with the second insulation film and the like. Subsequently, after the second insulation film and the like is provided onto the first wire pad portion, the recess for the second wire is then formed by etching and removing the second insulation film, the mask member, and the like so as to be connected to the contact hole. Even by these steps, similar to the cases of the individual first to fourth embodiments, the desired contact hole(s) and the recess for the second wire can be formed.

[0133] Still alternatively, after the second insulation film and the like are provided onto the first wire pad portion, a predetermined portion of the first wire pad portion is etched together with the second insulation film and the like existing thereon. Thereby, a desired contact hole can be formed in the state where substantially no events occur in which the inner portion of the contact hole is filled with the second insulation film and the like. Thereafter, the second insulation film, the mask member, and the like are etched and removed, and the recess for the second wire is thereby formed so as to be connected to the contact hole. Even by these steps, similar to the cases of the individual first to fourth embodiments, the desired contact hole(s) and the recess for the second wire can be formed.

[0134] Additional advantages and modifications will readily occur to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details and representative embodiments shown and described herein. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents. 

What is claimed is:
 1. A semiconductor device comprising: a first wire and a pad portion thereof provided in a portion from an upper surface to an inner portion of a first insulation film provided above a substrate; a second insulation film provided on the first insulation film and the first wire; a second wire provided to be exposed from an upper surface of the second insulation film in an upper portion of the pad portion of the first wire; and a contact plug provided to reach an inner portion of the pad portion of the first wire from an undersurface of the second wire.
 2. The device according to claim 1, wherein at least a side portion of the contact plug is electrically connected to the pad portion of the first wire.
 3. The device according to claim 1, wherein the second wire is provided with a pad portion having an undersurface spaced apart from the upper surface of the pad portion of the first wire.
 4. The device according to claim 1, wherein the contact plug is formed integrally with the second wire.
 5. The device according to claim 1, wherein the second wire and the contact plug are formed of at least one of an aluminium monomer and a compound containing aluminium.
 6. The device according to claim 1, wherein a plurality of the contact plugs are provided.
 7. The device according to claim 2, wherein the contact plug is provided with a lower end portion positioned at a height that is the same as or lower than that of the undersurface of the pad portion of the first wire.
 8. The device according to claim 3, wherein the second insulation film is sandwiched between the undersurface of the pad portion of the second wire and the upper surface of the pad portion of the first wire.
 9. A manufacturing method of a semiconductor device, comprising: forming a recess for a first wire and a recess for a pad portion of the first wire; forming the recess for the first wire in a portion from an upper surface of a first insulation film provided above a substrate to an inner portion thereof; forming the recess for the pad portion of the first wire in continuation to the recess for the first wire while selectively leaving the first insulation film; forming the first wire and the pad portion of the first wire by burying a first conductive material into inner portions of the recess for the first wire and the recess for the pad portion of the first wire; providing a second insulation film onto the first insulation film wherein the first wire and the pad portion of the first wire are formed; forming a recess for a second wire and a contact hole by removing the second insulation film on the pad portion of the first wire and the first insulation film selectively left; and forming the second wire and a contact plug by burying a second conductive material into inner portions of the recess for a second wire and the contact hole.
 10. The manufacturing method according to claim 9, wherein the contact plug is formed integrally with the second wire.
 11. The manufacturing method according to claim 9, wherein forming the recess for the pad portion of the first wire, the size of the first insulation film selectively left is slightly larger than the size of the contact hole.
 12. The manufacturing method according to claim 9, wherein the second wire and the contact plug are formed of at least one of an aluminium monomer and a compound containing aluminium.
 13. The manufacturing method according to claim 9, wherein the second wire is formed by pattering the second conductive material or a third conductive material.
 14. A manufacturing method of a semiconductor device, comprising: forming a recess for a first wire and a recess for a pad portion of the first wire; forming the recess for the first wire in a portion from an upper surface of a first insulation film provided above a substrate to an inner portion thereof; forming the recess for the pad portion of the first wire in continuation to the recess for the first wire while the first insulation film is selectively left; forming the first wire and the pad portion of the first wire by burying a first conductive material into inner portions of the recess for the first wire and the recess for the pad portion of the first wire; providing a second insulation film onto the first insulation film wherein the first wire and the pad portion of the first wire are formed; forming a contact hole by removing the first insulation film selectively left and second insulation film existing thereon; forming a contact plug by burying a second conductive material into an inner portion of the contact hole; providing a third insulation film on the second insulation film wherein the contact plug is formed; forming a recess for the second wire by removing the third insulation film existing on the pad portion of the first wire such that an upper surface of the contact plug is exposed; and forming the second wire by burying a third conductive material into an inner portion of the recess for the second wire.
 15. The method according to claim 14, wherein forming the recess for the pad portion of the first wire, the size of the first insulation film selectively left is slightly smaller than the size of the contact hole.
 16. The method according to claim 14, wherein the same conductive material is used as the second conductive material and the third conductive material.
 17. The method according to claim 14, wherein the second wire and the contact plug are formed of at least one of an aluminium monomer and a compound containing aluminium.
 18. The method according to claim 14, wherein the second wire is formed by pattering the second conductive material or a third conductive material. 